Until the advent of digital photographs, each print of a photo was in a real sense "an original." The detail and quality of the photo were established at the time the camera clicked and recorded the information. But almost as soon as people began making photographs, they also began using a variety of techniques to manipulate and change the images either during the development stage or after by compositing two or more photographs into one. Recognizing this ability to make post-production changes to existing photographs, if a photo was to be used as evidence, the law usually required testimony from the original photographer, who was expected to testify as to the provenance of the photo. Provenance is defined as the history of ownership and is usually expanded to include any changes to an item of historical value.
A commentator to one of my posts about photography recently raised the question of how his "pedigree was going to be affected if a photo was cropped or edited?" The question itself shows a lack of appreciation for the need to preserve the original photograph, but the question does need a response.
Once again, I will start with a hypothetical situation. What if your ancestor's family included six children? However, for whatever reason, the sixth child was not recorded in the family record because she died as an infant. However, there was a photograph made of the family shortly after the baby was born, showing the mother holding the infant. Let's further assume, because of the feelings of other family members or merely through carelessness, the mother, who was standing at the edge of the group being photographed, was cropped out of subsequent prints of the photo. After years of research, a genealogist finds a copy of the original photo showing the infant. Because of this new information, the sixth child is finally added to the family.
This example is not far fetched. Photographs can be valuable for establishing the age and identity of ancestors. But going back to my first example of using a photograph in court to prove a legal case, the photograph only becomes "evidence" if the provenance can be established and any changes to the photograph explained. Especially, with today's digital technology, photographs are not assumed to be evidence at all unless there is accompanying testimony as to the provenance and the relevance of the photo. Even if the photograph is being used only for demonstrative purposes, the witness must testify that the photograph fairly and accurately depicts the scene about which he or she is testifying.
The problem with the use of photos by genealogists is that there exist no "rules" such as the legal evidentiary rules, that govern the use of photographs even though adding a photo is automatically assumed to be helpful and sometimes necessary to "prove" a fact or relationship. In most genealogical treatises, photographs are added without any reference at all to the details of how or where or when the photo might have been taken. Obviously edited photos are included without any explanation as to what information has been removed. Not infrequently, people in the photos are mis-identified, leading to all sorts of unjustified conclusions. In short, photos are not usually subjected to the same standard as would be applied to an assertion of fact such as a marriage date or death date. Photos become genealogical evidence only to the extent that they are subject to the same Genealogical Proof Standard as any other fact or event asserted as evidence with a complete and accurate citation of source.
A photograph, at the moment it is taken, contains all the information is will ever have. Any alteration of that photo, in any way, reduces the amount of information contained in the original. Editing photographs that are intended to be used as genealogical evidence is unacceptable, just as altering a birth date or death date would be.